Conventional materials for optical parts of optical devices are glass, plastics and single crystals of, for example, lithium niobate (LiNbO3) as described in Japanese Unexamined Patent Application Publication Nos. 5-107467 and No. 9-245364.
Such glass and plastics have a high light transmittance, can easily be processed into devices and are used as optical parts such as lenses. The single crystalline LiNbO3 has some electrochemical properties and exhibits double refraction and is used as an optical part such as an optical waveguide utilizing these properties. Demands have been made on further miniaturized or slimmed optical pickups and other optical devices using these optical parts.
However, the conventional glass has a refractive index less than 1.9, and the resulting optical parts and optical devices using the same have the limitations in miniaturization and slimming. The plastics have low moisture resistance and a low refractive index, exhibit double refraction and cannot efficiently transmit and condense incident light. The single crystals of, for example, LiNbO3 have a high refractive index of, for example, 2.3 but exhibit double refraction, are difficult to use as the optical parts such as lenses and have the limitations in their application.